Is Baby Brain Real? Pregnancy Changes Whopping 95% of Gray Matter

Almost all of the gray matter in the brains of women changes during pregnancy, according to a recent study, and these changes are linked to hormone fluctuations and the psychological wellbeing of mothers after giving birth. Neuroscientists tested the effects of pregnancy and motherhood on the brains of nearly 180 women using magnetic resonance imaging (MRI) scans. They compared what happened to the brains of women who became pregnant for the first time with those of women whose partners were carrying their babies, so who experienced motherhood for the first time without being pregnant themselves. This was to distinguish between biological changes that happened during pregnancy from those that happened due to the experience of becoming a mother. Every year, approximately 3.7 million women give birth, according to data from the Centers for Disease Control and Prevention (CDC) from 2022.

Neuroscientists at the Universitat Autònoma de Barcelona (UAB), Spain—together with the Gregorio Marañón Health Research Institute, the Hospital del Mar Research Institute, and international institutions—took MRI scans of the women's brains before pregnancy, during the second and third trimester of pregnancy, and six months after giving birth. They found that 94 percent of the total gray matter in the brains of the pregnant women changed during pregnancy. Gray matter is an essential type of tissue in the brain and spinal cord that plays a key role in memory, emotions, movement and sensory perception, and makes up just less than half of the brain. The neuroscientists found that gray matter volume was reduced by up to 4.9 percent during pregnancy. These changes particularly affected areas of the brain linked to social cognition; in the default mode network, linked to daydreaming, introspection and recalling memories; and in the frontoparietal network, linked to problem solving and decision-making. But they were not permanent; the neuroscientists also observed that most of the neurological changes were reversed postpartum. The scientists linked the changes with fluctuations of two different forms of the sex hormone estrogen—estriol-3-sulfate and estrone-sulfate—that increase exponentially during pregnancy and return to baseline levels after giving birth. Women who experienced greater increases and decreases in these hormones also seemed to experience greater brain changes and recovery of gray matter volume later on. After giving birth, women whose brains had recovered more of their gray matter volume reported better mental health and bonding with their babies too. Is there a health problem that's worrying you? Do you have a question about pregnancy? Let us know via health@newsweek.com. We can ask experts for advice and your story could be featured in Newsweek.

Reference

Servin-Barthet, C., Martínez-García, M., Paternina-Die, M., Marcos-Vidal, L., de Blas, D. M., Soler, S., Khymenets, O., Bergé, D., Casals, G., Prats, P., Pozo, O. J., Pretus, C., Carmona, S., Vilarroya, O. (2025). Pregnancy entails a U-shaped trajectory in human brain structure linked to hormones and maternal attachment, Nature Communications, 16(730). https://doi.org/10.1038/s41467-025-55830-0